Intravascular catheter having combined imaging abrasion head

ABSTRACT

Front-end and side-on intravascular catheters are described that comprise an abrasive head contained substantially within a housing. Aspiration means and flushing means are connected to the region of grinding to remove dislodged debris. A preferred embodiment has the abrasive surface of a rotatable head comprised of diamond powder. Another preferred embodiment has an ultrasonic transducer affixed to the head to permit transluminal imaging of the site of occlusion.

This is a continuation of application Ser. No. 08/293,831, filed on Aug.22, 1994 and now U.S. Pat. No. 5,507,292, which is in turn acontinuation of U.S. application Ser. No. 07/842,813, filed on Feb. 27,1992, now U.S. Pat. No. 5,402,790, which is in turn a continuation ofU.S. application Ser. No. 526,413, filed on May 21, 1990, now U.S. Pat.No. 5,100,424.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to vascular catheters. Moreparticularly, the present invention relates to atherectomy catheterscapable of performing abrasion atherectomy, optionally in combinationwith transluminal imaging.

The blood vessels of human beings commonly become constricted due to thedeposition of fatty substances, e.g., lipoproteins, on the interior ofthe vessel walls. This condition, known as arteriosclerosis, oratherosclerosis, occurs naturally as a part of the aging process. Thecondition may also be promoted by such factors as heredity, diet,hypertension, and cigarette smoke. The vascular deposits result in arestriction of blood flow and in serious cases can place a person'shealth at risk. In acute cases the restriction can result in stroke,hemorrhage, etc. Initially, the fatty deposits are relatively soft;however, over time they become fibrotic and hardened.

Numerous approaches for reducing and removing intravascular depositshave been proposed. The deposits, called atheromas or atheroscleroticplaques, can be reshaped by dilatation of an inflatable balloon locatedat the distal end of an angioplasty catheter.

Alternatively, atheromas can be removed from the vessel wall by cutting,grinding, or thermal ablation, e.g., via laser angioplasty. Ofparticular interest to the present invention are atherectomy cathetersthat remove atheromas from the vessel wall by cutting or grinding.

In a typical atherectomy operation, a catheter of appropriate diameteris introduced into a patient's vascular system and positioned adjacentthe occluding atheroma. The distal end of the catheter is provided witha blade which is brought into contact with the atheroma. The cathetermay either be a terminal (front-end) cutting type or a side-cuttingtype. Side-cutting atherectomy catheters frequently employ an inflatableballoon located opposite the blade to firmly engage the blade with theatheroma.

However, the above devices have certain deficiencies. In particular, theblades of the cutting element may slice into too much of the occludingmaterial at one time, thereby causing release of large emboli and/orrupture of the vessel wall. Moreover, if the emboli are not promptlycaptured and removed from the patient's body, they may pass through thevascular system until they become wedged in narrow points of thevascular channels. If an embolus becomes lodged in a critical region ofthe vascular system, e.g., a coronary artery, the patient's health canbe placed seriously at risk.

The release of large emboli into the vascular system is particularlyproblematic when front-end catheters are employed. Front-end devicesgenerally employ a cutting element which extends beyond the distal endof a casing for the cutting element. See, for example, U.S. Pat. No.4,857,046. Thus, relatively large particles can be dislodged from theatheroma. Additionally, the dislodged particles generally remain outsidethe casing of the cutting element, free from entrapment by the catheter.If such particles are not promptly collected they will circulate freelythrough the vascular system as emboli.

Side-cutting catheters generally reduce the likelihood that emboli willbe released into the vascular system since the housing in which theblades are at least partially contained can passively collect dislodgedparticles. The collected particles can be removed from the patient'svascular system upon retraction of the catheter. See, U.S. Pat. No.4,794,931. However, many particles can be expected to escape entrapmentwithin the catheter in such a device.

Several methods have been proposed for remedying the shortcomingsidentified above one approach is to modify the impacting head in orderto channel dislodged particles into the catheter. See, for example, U.S.Pat. No. 4,857,046 which describes an auger-like mechanism forcollecting particles. Another approach is to provide an aspiration meansfor actively removing particles from the vascular system. See, forexample, U.S. Pat. No. 4,857,045. Still other approaches involvemodifying the impacting head to reduce the size of the dislodgedparticles in an effort to minimize the risk to the patient presented bylarge emboli. See, for example, FIG. 4 of U.S. Pat. No. 4,857,045. Noneof the approaches proposed for reducing the size of particles and forcapturing and withdrawing the particles provides a satisfactory solutionfor these problems.

For these reasons it is desirable to provide catheters that grindatheromas into very small debris particles. Also, it is desirable toremove those particles via catheters provided with flushing andaspiration means for removing the particles. Such devices are expectedto significantly reduce the potential for release of large emboli.Additionally, it is desired to provide a means for transluminallyimaging the site of atherectomy in order to determine the location andextent of removal of the undesired tissue.

2. Description of the Background Art

U.S. Pat. Nos. 4,857,046, 4,857,045, 4,842,578, 4,747,821, 4,631,052,and 4,795,438 all describe front-end intravascular catheter devices.None of the references describe devices that grind away atheroscleroticplaques via an impacting head that is substantially contained within ahousing. Nor do the devices utilize an inflatable balloon means to aidengagement of the impacting head with the undesired tissue. U.S. Pat.No. 4,794,931 describes a catheter having a rotary impacting head whichremoves sclerotic material through a side window provided in a housing.An opposing balloon is provided to assist placement of the head adjacentthe undesired material. U.S. Pat. Nos. 4,794,928; 4,465,072; and3,889,657 relate to catheter designs intended to scrape blood vesselsand other body lumens.

Various techniques for transluminal imaging of the diseased region of avessel wall have been proposed, including endoscopic and ultrasonicimaging techniques. See, for example, U.S. Pat. No. 4,794,931 whichdescribes an ultrasonic transducer attached to the hub of a rotary head.See, also, commonly-assigned copending application Ser. No. 366,906which describes a laser catheter having transluminal imaging capability,and copending application Ser. No. 500,641 which describes a combinedballoon angioplasty/imaging catheter.

SUMMARY OF THE INVENTION

According to the present invention, intravascular catheters for removingstenotic material from a patient's vascular system comprise an elongatecatheter body having proximal and distal ends. A housing is secured tothe distal end of the catheter body and the housing is provided with anaperture in one of its side walls. A head for abrading stenotic materialis provided substantially within the housing so that any material thatpenetrates the aperture can be abraded and captured within the housing.Dislodged material is withdrawn from within the housing by means forwithdrawing the material provided internal the catheter.

A preferred embodiment of the invention has an aspirating meansconnected to the interior of the housing via an axial lumen provided inthe catheter body. Abraded stenotic material is thereby aspirated fromthe patient's body. Additionally, grooves (or channels) may be providedaxially or helically along the exterior of the abrasive head or alongthe interior wall of the housing. Such grooves assist in transport ofabraded material from distal the head to points proximal the head. Aflushing means located external the patient's body may also be employedto augment removal of material from within the catheter housing.

Another preferred embodiment has a transluminal imaging means affixed tothe head for abrading the stenotic material. Preferably, thetransluminal imaging means is afforded by an ultrasonic transducer.

A further preferred embodiment of the invention employs at least oneinflatable balloon attached to the housing. Inflation of the balloon(s)assists in contacting the stenotic material with the abrasive head whenthe housing aperture is provided in a side wall of the housing.

A still further preferred embodiment of the invention employs arotatable member substantially within the housing for abrading stenoticmaterial that penetrates the housing aperture. Placement of the rotarymember within the housing helps ensure that dislodged particles collectinside the-housing. The rotatable member is able to abrade stenoticmaterial, e.g., by provision of an abrasive surface. Exemplary surfacesof the rotatable member are comprised of diamond powder and fusedsilica, tungsten carbide, aluminum oxide, boron carbide, and the like.The rotatable member can have an axial lumen through which a guidewiremay be passed. Imaging of the site of occlusion may be provided by anultrasonic transducer affixed to the rotatable member.

The present invention affords novel methods for removing stenoticmaterial from a patient's vascular system. The methods comprise thesteps of introducing the distal end of a catheter into the vascularsystem and positioning the aperture of the housing located at the distalend of the catheter body proximate the stenotic material. An abrasivemember located substantially within the housing is engaged against thestenotic material through translational and/or rotational motion of theabrasive member. Abraded material is withdrawn from the patient's bodyvia means for withdrawing the material, e.g., by aspiration of theregion within the housing.

The present invention thereby affords superior grinding devices andmethods for removing stenotic material from a patient's vascular system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a detail view of the distal region of a front-end catheterconstructed in accordance with the principles of the present invention.

FIG. 2 is a detail view of the distal region of a side-on catheterconstructed in accordance with the principles of the present invention.

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1.

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 2.

FIG. 5 is a cross-sectional view of an alternative housing embodimentconstructed in accordance with the principles of the present invention.

FIGS. 6A-D present perspective and end-on views of exemplary front-endabrasive heads constructed according to the principles of the presentinvention.

FIGS. 7A-E present perspective views of exemplary side-on abrasive headsconstructed according to the principles of the present invention.

FIGS. 8A-C show cross-sectional views of alternative catheter bodiesconstructed according to the principles of the present invention (FIG.8A is taken along line 8--8 of FIG. 2).

FIG. 9 is a detail view of a side-on catheter having an alternativedesign for provision of means for withdrawing abraded material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the present invention, intravascular catheters will includean elongated catheter body having distal and proximal ends. The catheterbody will include an abrasive head for abrading stenotic material at thedistal end of the catheter body. Preferably, the abrasive head will beprovided by an abrasive rotatable member contained substantially withinthe housing. The housing will be provided with an aperture to permitintrusion of the stenotic material into the housing cavity. At leastpart of the periphery of the aperture is expected to contact targetstenotic material during operation of the abrasive head, therebyassisting in containment of particles released by the grinding process.Also, means for withdrawing abraded material from within the housing toa point external the patient is provided. Preferably, an aspiratingmeans in communication with the interior of the housing via an axiallumen in the catheter body will be employed as the means for withdrawingabraded material.

In a preferred embodiment, the aperture of the housing located at thedistal end of the catheter will be provided in a side wall of thehousing. One or more inflatable balloons will be optionally providedopposite the aperture to permit anchoring the distal end of the catheteradjacent a target stenosis.

The stenotic material that can be abraded by the present devicesincludes all naturally occurring occlusions of vascular walls, e.g.,atherosclerotic plaques, lipoprotein deposits, blood clots, hemorrhagedtissues, etc.

Catheters constructed according to the present invention also mayinclude a transluminal imaging means affixed to the abrasive head. Suchimaging means preferably will be provided by ultrasonic transducers.Suitable transducers are described in U.S. Pat. No. 4,794,931, which isincorporated herein by reference.

A. Catheter Bodies.

The vascular catheters of the present invention will comprise a catheterbody having distal and proximal ends. The catheter body will be flexibleto permit its passage through the vascular system of a patient.Preferably the catheter body will be comprised of a flexible transparentthermoplastic that affords ready visual inspection for air bubblesinside the catheter body. The catheter-body will preferably have asmooth tubular shape; however, the catheter body may have a ridgedstructure, particularly when it is desired to provide a lumen, e.g., aguidewire lumen, along the longitudinal axis of the catheter.

The catheter selected will have an outer diameter small enough to permitpositioning adjacent the diseased region of the vessel wall. Typically,the outer diameter of catheters employed will be in the range from about1 mm to 4 mm, usually being about 2.5 mm for peripheral arteries ofadult humans and about 1.7 mm for coronary arteries. Catheters employedwill typically have a length ranging from about 60 cm to 150 cm.

Referring now to FIG. 1, a front-end type vascular catheter constructedin accordance with the principles of the present invention includes anelongated catheter body 110 having distal 112 and proximal 114 ends.Catheter body 110 is connected at its proximal end 114 to a manifold(not shown) via manifold connector 116. Such manifold connector includesinternally-threaded means for connecting catheter body 110 to themanifold and is well known to those skilled in the art. The distal endof the catheter may be adapted to accept a moveable guidewire, describedmore fully herein below.

Catheter body 110 is comprised of a flexible plastic tube 118 having anouter diameter suitable for insertion into the patient's target vessel.Plastic tube 118 is preferably comprised of a transparent thermoplasticto permit observation of air bubbles internal the tube. Tube 118 isflexible and includes at least one lumen extending from the distal end112 to the proximal end 114 thereof. Additional lumens may be includedas needed. The utility of such lumens is discussed in more detail below.

Catheter body 110 is provided at its distal end with housing 120.Housing 120 preferably is constructed from stainless steel and isattached to plastic tube 118 using conventional methods. See, forexample, U.S. patent application Ser. Nos. 732,691 and 834,893 (now U.S.Pat. No. 4,794,931). In front-end type catheters an aperture 122 isprovided in the distal tip of housing 120 to permit penetration oftarget stenotic material into housing cavity 124. Housing cavity 124contains all void space within housing 120 and is defined at its distalend by the periphery of aperture 122 and at its proximal end by flexibletube 118. Abrasive head 126 is provided internal housing 120 and iscapable of moving axially or rotationally within housing cavity 124. Across-section of housing 120 along line 3--3 is presented in FIG. 3,which is discussed herein below.

FIG. 2 shows the distal region of a side-on catheter constructed inaccordance with the principles of the present invention. Catheter body210 has essentially the same dimensions and is constructed fromessentially the same materials as front-end catheter bodies describedabove. Catheter body 210 has distal end 212 and proximal end 214thereof. Proximal end 214 is connected to a conventional manifoldconnector (not shown). A conventional fixed guidewire 215, describedmore fully herein below, is secured to distal end 212. Flexible tube 216is comprised of the same materials and has essentially the sameconfigurations allowed for the corresponding tube for front-endcatheters described above.

Flexible tube 216 is attached to housing 218 in conventional manner.Housing 218 is typically comprised of stainless steel and has acylindrical shape. A portion of the sidewall of housing 218 is removedto present aperture 220, through which stenotic material may penetrateinto housing cavity 222. The distal tip of housing 218 may optionally beprovided with an orifice through which a guidewire can pass.

In a preferred embodiment, at least one inflatable balloon is providedexternal the housing so as to press the side of the housing having theaperture against the target stenotic material. For example, as shown inFIG. 2, inflatable balloon 224 is provided opposite aperture 220 andexternal to housing 218. Balloon 224 is securely attached to housing218, e.g., via a suitable adhesive. The proximal extremity of balloon224 is preferably bonded to flexible tube 216 via a heat-shrinkablematerial. Balloon 224 can be inflated by passing an inflation mediumthrough an inflation orifice 226 provided proximate the proximalextremity of balloon 224. Other aspects of the inflatable balloonfeature of side-on catheters are presented in U.S. Pat. No. 4,794,931and are incorporated herein by reference.

FIG. 4 presents a cross-sectional view of the side-on catheter of FIG. 2taken along line 4--4 thereof. Thus, housing 218 defines housing cavity222 and is provided with aperture 220 with balloon 224 provided oppositeaperture 220.

B. Abrasive Heads.

In the present invention, an abrasive head is provided at the distal endof the catheter body. The head is contained substantially within thehousing located at the distal end of the catheter body. It iscontemplated that a portion of the abrasive head may extend from withinthe housing to a point beyond the aperture provided in the housing;however, the entirety of the head will be contained within the housingsufficiently to ensure that dislodged stenotic material will besubstantially contained within the housing.

The abrasive head may be comprised of a unitary abrasive material or maybe a composite of a support material and an abrasive surface materialaffixed to the support. When an abrasive surface material is employed itmay be adhesively bonded to the support by methods well known to thoseskilled in the art. Preferred abrasive materials comprising the surfaceof the abrasive head include fused silica, diamond powder, tungstencarbide, aluminum oxide, boron carbide, and other ceramic materials.Suitable abrasive materials are available commercially from NortonCompany, Worcester, Mass.

When a composite abrasive surface and solid support is employed as theabrasive head of the present invention, a suitable support material mustbe identified. Generally, a suitable support will be any solid materialthat bonds effectively to the abrasive surface material with anadhesive. The support further must withstand the inertial and impactforces experienced during operation of the abrasive head.

A preferred support material is stainless steel. Also, the supportpreferably has an axial lumen to allow passage of a guidewiretherethrough.

Typically, the abrasive head is attached to a drive means via a couplingprovided at its proximal end. The drive means will extend axiallythrough a lumen provided in the catheter body to a point external thepatient's body. The drive means is connected to a drive motor whichprovides the power for driving the abrasive head. The drive meanspreferably includes an internal lumen which permits passage of aguidewire if desired.

Operation of the drive means is such that one revolution of the drivemeans causes one revolution of the abrasive head. During operation, thedrive means will usually make 200-100,000 revolutions per minute. Also,translation of the drive means relative to the catheter body causes atranslation of the abrasive head relative to the catheter body.Translation and rotation of the abrasive head via the drive means isafforded so as to permit the head to contact stenotic material thatpenetrates the aperture of the housing. The construction and operationof drive means suitable for use in the present invention is furtherdescribed in U.S. Pat. No. 4,794,931, which is incorporated by referenceherein.

1. Front-end Catheters

When the catheter is of the front-end type, the abrasive head containedsubstantially within the housing will have an abrasive surface at thedistal-most end of the head. Abrasive surfaces may also be providedelsewhere on the head. The proximal-most end of the head is incommunication with a means for driving the head, e.g., a drive cable ora compressed fluid means.

FIG. 3 presents a cross-sectional view of the head and housing of thefront-end type catheter shown in FIG. 1. Thus, an abrasive rotatablemember 126 is provided internal housing 120 and is positioned so as topermit engaging rotatable member 124 with any stenotic material thatpenetrates the aperture 122 in the distal end 112 of housing 120. Therotatable member 126 need not be wholly contained within housing 120,i.e., the most distal region of the rotatable member may extend throughaperture 122; however, rotatable member 126 must remain sufficientlywithin housing 120 such that the abrading surface of the rotatablemember remains substantially within housing cavity 124 defined at itsmost distal end by aperture 122.

Grooves (or channels) are optionally provided axially along the exteriorwall of the abrasive head to assist passage of dislodged material fromthe distalmost end of the housing to a point proximal the head. Forexample, FIG. 3 shows an abrasive rotatable member 126 provided withinhousing 120. The outer periphery of rotatable member 126 is providedwith two grooves 128. An abrasive head having grooves may have only onegroove or may have a plurality of grooves. Preferably, the grooves willbe spaced equally about the periphery of the head; however, such equalspacing is not necessary. Abrasive rotatable member 126 is also providedwith lumen 130 which permits passage of a guidewire therethrough and mayalso assist in the withdrawal of released particles from the distalregion of the head.

Grooves may additionally or optionally be provided axially along theinterior surface of the housing. For example, FIG. 5 shows across-sectional view of an exemplary housing 510 having four equallyspaced grooves 512 along the interior surface of housing 510. The sameor similar designs having housings provided with interior grooves arealso suitable for side-on catheters. The grooves or channels willusually be oriented in a generally axial direction but it will also bepossible to dispose the grooves helically so long as they provide orallow for proximal translation of the abraded material passed the head.

Referring now to FIGS. 6A-D some exemplary front-end abrasive heads inaccordance with the principles of the present invention are presented.Both side views and end-on views are presented. Other abrasive headsconsistent with the principles of the present invention will be apparentto those skilled in the art.

FIG. 6A shows head 610 having a cylindrical body 612 capped at itsdistal end by a rounded, e.g., hemispherical, abrasive surface 614,cylindrical body 612 is provided with four periodic grooves 616 whichpermit withdrawing abraded material from a region distal the head to aregion proximal the head. An end-on view of the head shows the abrasivesurface 618 periodically grooved around its periphery. Drive means 620is attached to the proximal end of head 610 and extends proximally to apoint external the patient's body.

FIG. 6B shows an alternative head design in which head 630 has acylindrical body and a concave depression 632 provided at its distalend. An end-on view of head 630 shows an abrasive surface 634 having acircular periphery and an orifice 636 provided central to the surfacethrough which a guidewire (not shown) may pass. Preferably, when aguidewire is employed, the wire will pass through the interior of head630 via orifice 636 and will extend through an axial lumen providedinterior drive means 620. The concave design of this and other suchheads is expected to further assist in containing particles releasedupon grinding.

FIG. 6C shows another embodiment of an abrasive rotatable member of thepresent invention. Rotatable member 640 has a cylindrical body in whichperiodic grooves 642 are axially provided. The distal ends 644 ofrotatable member 640 has a recessed abrasive surface 646. The peripheryof abrasive surface 646 is grooved at points corresponding to periodicgrooves 642.

FIG. 6D presents a further embodiment of an abrasive rotatable memberaccording to the principles of the present invention. Rotatable head 650has a substantially cylindrical body provided with periodic grooves 652running axially along its surface. The distal end 654 of head 650 has asubstantially planar abrasive surface 656 attached thereto. Theperiphery of surface 656 has indentations accommodating periodic grooves652. The center of surface 656 is provided with orifice 658 throughwhich a guidewire may pass. Imaging transducer 660, e.g., an ultrasonictransducer, is affixed to surface 656.

2. Side-on Catheters

The abrasive heads of the present invention that are suitable for use inside-on catheters are comprised of the same or similar materials and areconstructed analogously to the heads described above for front-endcatheters. However, the side-on catheters of the present invention canbe contrasted from front-end designs in that side-on designs allow useof a pull-type abrasive head, in which an abrasive surface is providedon the proximal end of the head.

Referring now to FIG. 2, housing 218 is provided with aperture 220.Preferably, aperture 220 is provided as an elongated slit in housing218. Housing 218 further defines internal region 224 in which anabrasive head (not shown) will be provided. Moreover, internal region224 will be at least partially occupied by target stenotic material anddebris during operation of the device. Inflatable balloon 222 isprovided opposite aperture 220 and external to housing 218. Duringinflation of inflatable balloon 222, an inflation medium is passed intoballoon interior 228 provided between balloon 222 and housing 218.Likewise, deflation of balloon 222 occurs upon removal of inflationmedium from the balloon interior 228. Inflation and deflation operationsare described more fully below.

Referring now to FIGS. 7A-E, exemplary side-on abrasive heads arepresented. Thus, in FIG. 7A, abrasive head 710 is comprised of acylindrical region 712 and a conical region 714 distal to thecylindrical region. Conical region 714 is provided with an abrasivesurface, which preferably extends over the entirety of the conicalregion. The cylindrical region 712 of head 710 is provided with periodicgrooves 716 which allow passage of particles and fluid from distal head710 to proximal head 710. Orifice 718 is provided in the distal tip ofconical region 714 to allow passage of a guidewire. Drive means 720 isattached proximally to head 710 to allow translation and/or rotation ofhead 710 to contact the abrasive surface of the head against stenoticmaterial.

FIG. 7B depicts another preferred embodiment of an abrasive headsuitable for removing stenotic material via a side-on atherectomycatheter. Thus, the head is comprised of cylindrical region 722proximally attached to conical region 724. Conical region 724 has anabrasive surface, preferably extending over the entirety of region 724.The proximal-most tip of conical region 724 is attached to drive means720.

FIG. 7C presents a further preferred embodiment of a side-on abrasivehead. Thus, the head comprises cylindrical region 730 attached at itsdistal and proximal ends to conical regions 732 and 734, respectively.Both regions 732 and 734 are provided with abrasive surfaces.Cylindrical region 730 is provided with periodic grooves 736 and isfurther provided with transducer 738. The proximal terminus of region734 is attached to drive means 720.

FIG. 7D shows a further preferred embodiment of a suitable side-onabrasive head in which an abrasive surface is provided over at leastpart of cylindrical region 740. Cylindrical region 740 is furtherprovided with periodic grooves 742 as described above. Transducer 744 isprovided in a recess on the surface of region 740.

In FIG. 7E, the abrasive head is comprised of two conjoined abrasiveregions. Thus, cylindrical region 750 is joined to conical region 752provided distally to cylindrical region 750. Groove 754 is providedaxially along cylindrical region 750.

Clearly, other designs of abrasive heads are contemplated in accordancewith the principles of the present invention. Such designs will bereadily apparent to one skilled in the art.

C. Means for Withdrawing Material

A means for withdrawing dislodged stenotic material from within thehousing for the abrasive head is provided internal the catheter. Suchprovision permits removal of debris generated by the grinding processsoon after it is produced, thereby greatly reducing the likelihood ofemboli being released into the vascular system. Provision of suchwithdrawing means integrally to the catheter body also precludes theneed for a means for withdrawing debris that is independent of thecatheter.

Generally, the means for withdrawing abraded material will be the samefor front-end or side-on catheters. However, some distinctions betweenfront-end and side-on embodiments with respect to provision of thewithdrawing means are envisioned and are described below.

Preferably, the means for withdrawing abraded stenotic material willprincipally employ an aspiration means in communication with the housingchamber internal the housing. Such means will ensure a negative pressureis maintained within the housing chamber relative to the surroundingvascular system, thereby minimizing the chance of emboli release fromthe housing chamber. The location selected for the aspiration openingwithin the housing is noncritical; however, it will preferably be distalthe housing chamber and relatively near the aperture of the housing inorder to minimize the time abraded material is retained within thehousing.

Additionally, the means for withdrawing abraded material from thehousing chamber may include a flushing means in communication with thechamber. The flushing means will employ a biocompatible flushing medium.Suitable flushing media are well-known to those skilled in the art andinclude saline and electrolyte solutions.

Care must be taken to ensure that the introduction of flushing mediainto the region internal the housing does not significantly promoterelease of emboli into the vascular system. Since release of emboli fromwithin the housing will most likely occur through the aperture of thehousing, flushing media will preferably be introduced into the housingchamber at a point within the housing that is as distant from theaperture as possible.

Further, it is preferred that the point selected within the housing forintroducing the flushing medium will be chosen so as to maximize thecoverage, or "sweep," of flushing media throughout the interior of thehousing. Such provision will favor separation of the introduction pointof the flushing medium from the point selected for the aspirationopening.

An exemplary preferred embodiment of the above-described means forwithdrawing abraded material is presented in FIG. 9. Thus, the distalregion 910 of a side-on catheter has flexible tube 912 attached tohousing 914. Housing 914 is provided with an aperture 916 and withinflatable balloon 918 located opposite the aperture. Abrasive head 920is located in housing chamber 922 internal housing 914 and is connectedat its proximal end to drive means 924. Drive means 924 extendsproximally through a lumen provided in flexible tube 912. A moveableguidewire will pass through a lumen provided internal in drive means924. The guidewire will extend through the entire length of catheter 910and will extend proximally and distally therefrom, as described morefully herein below.

An inflation medium will be introduced into catheter 910 via inflationlumen 926 provided in flexible tube 912. The inflation medium will passthrough orifice 928 provided at the proximal extremity of housing 914and into inflation region 930 located between balloon 918 and housing914.

Flexible tube 912 is further provided with aspiration lumen 932 whichextends axially therethrough and terminates distally in aspirationorifice 934 located at the interface between housing chamber 922 andflexible tube 912. Flexible tube 912 is further provided axially withflushing lumen 936 which extends distally to the proximal end offlushing tube 938 provided within housing chamber 922. Flushing tube 938and flushing lumen 936 are met so as to prevent leakage of flushingmedium there between. Flushing medium will pass through a lumen providedin flushing tube 938 until reaching flushing orifice 940 locateddistally in housing chamber 922.

Other embodiments incorporating the means for withdrawing abradedmaterial from within the housing will be apparent to the skilledpractitioner in view of the principles of the present invention.

D. Imaging Transducers

Frequently, an imaging means will be employed to afford a transluminalimage of a diseased region of the patient's vascular system. Preferably,an ultrasonic transducer will be used to generate the imaging medium. Apreferred transducer, its associated circuitry, and a preferred mode ofoperation are described in U.S. Pat. No. 4,794,931, incorporated hereinby reference.

For example, FIG. 7D shows a cylindrical abrasive head suitable for usein a side-on catheter device according to the principles of the presentinvention. Transducer 744 is attached to the exterior of abrasiverotatable member 740. The transducer 744 will preferably be positionedin a recess provided in the surface of member 740. The recess will besufficient to ensure that transducer 744 does not interfere withabrasion of atheromic material. Typically, transducer means 744 will becircular in shape and will have an outer diameter of 0.025-0.100 inches.

E. Guidewires

The catheters of the present invention will usually be used inconjunction with a guidewire. The guidewire will be either a fixed ormoveable type. When a fixed guidewire is used, the distal end of thecatheter will be secured to the guidewire. The guidewire will help toidentify the vascular channel through which the catheter will pass,thereby assisting in placement of the distal end of the catheteradjacent stenotic material.

When a moveable guidewire is employed the guidewire will be firstinserted into a patient's vascular system. The guidewire will pass tothe target stenotic material. The distal end of the catheter will beguided to the site of occlusion by the guidewire. Usually, the guidewirewill pass through an orifice provided in the distal tip of the catheterand will pass through the interior of the housing, typically via a lumenprovided in the abrasive head. The guidewire will extend proximallythrough a lumen provided for such purpose in the catheter until theguidewire exits the patient's body.

FIGS. 8A-C present cross-sectional views of exemplary catheter bodiesincorporating a lumen for passage of a guidewire therethrough. Forexample, FIG. 8A shows flexible tube 810 of the catheter body providedwith lumen 812. Lumen 812 affords passage of drive means 814 which isitself provided with guidewire lumen 816. Flexible tube 810 is furtherprovided with lumens 818, 820, and 822 which provide, respectively,means for aspirating dislodged material, means for flushing, and meansfor inflating an inflatable balloon.

A cross-sectional view of a catheter body having an alternative design,is shown in FIG. 8B. Thus, flexible tube 830 is provided with lumen 832which accommodates drive means 834. As shown, drive means 834 need nothave an axial lumen therethrough since the guidewire is passed through aseparate lumen in flexible tube 830. Flexible tube 830 is furtherprovided with lumens 836, 838, and 840 which allow, respectively,passage of a guidewire, aspirating means, and flushing means. Such adesign is preferred when an inflatable balloon need not be present,e.g., when a front-end type catheter is employed.

FIG. 8C shows a cross-sectional view of another preferred embodiment, inwhich the guidewire passes through a lumen provided in the flexible tubeof the catheter body. Thus, flexible tube 850 is provided with an axiallumen 852 which accepts drive means 854. Flexible tube 850 is furtherprovided with lumens 856, 858, 860, and 862 which permit, respectively,passage of a guidewire, aspiration means, flushing means, and inflationmeans.

Other lumen patterns are consistent with the principles of the presentinvention and will be apparent to one skilled in the art. The innerdiameter of a lumen provided for a guidewire will vary according to thediameter of the catheter but will typically be 0.0100.020 inches forsmaller catheters and 0.025-0.040 inches for larger catheters.

F. Method of Use

Preferably, the distal end of the catheter and its abrasive head will bepositioned adjacent target stenotic material with aid of X-rayfluoroscopy which readily identifies a catheter's location internal thepatient. Such methods are well-known to those skilled in the art.

When a side-on catheter is employed, an inflation balloon is preferablylocated opposite the target deposit to cause the material to penetratethe aperture of the housing containing the abrasive head. The abrasivesurface of the head will grind against the stenotic material through acombination of rotational and translational motion until the material iseffectively removed from the vessel wall. Debris generated by thegrinding process will be vacuum aspirated via an aspirating meansexternal the patient. Preferably, a flushing medium is provided toassist withdrawal of the particles. The site of occlusion is inspectedeither concurrent with or subsequent to the grinding process todetermine the extent of removal, preferably by means of an ultrasonictransducer located on the surface of the abrasive head. The above seriesof steps can be repeated at a different site of occlusion in the samemanner.

Although the foregoing invention has been described in detail forpurposes of clarity and understanding, it will be obvious that certainmodifications may be practiced within the scope of the appended claims.For example, catheters constructed according to the principles of thepresent invention may be equipped with two balloon members to betteranchor the catheter in the vascular system. Also, when two balloons areprovided, they may be offset from directly opposite the aperture of thehousing, thereby allowing removal of a portion of the housing directlyopposite the aperture. Such a configuration will allow imaging of thevessel wall directly opposite target stenoses.

What is claimed is:
 1. A method for removing stenotic material from apatient's vascular system comprising the steps of:introducing acatheter, said catheter having an abrasive member containedsubstantially within the catheter during positioning and abrasion, intothe vascular system; and contacting the stenotic material with saidabrasive member, whereby the stenotic material is abraded and collectedby the catheter.
 2. A method according to claim 1, wherein the abradedstenotic material is withdrawn from the housing by aspiration.
 3. Amethod according to claim 2, wherein the abraded stenotic material iswithdrawn from the housing by a combination of flushing and aspiration.4. A method according to claim 1, further comprising imaging thevascular system with an ultrasonic transducer, mounted on the abrasivemember.
 5. A method according to claim 1, further comprising inflatingat least one inflatable balloon attached to the housing so that thestenotic material penetrates the aperture of the housing.
 6. A methodaccording to claim 1, wherein the abrasive member is contacted bytranslation in combination with rotation.
 7. A method for removingstenotic material from a patient's vascular system comprising the stepsof:introducing a catheter, said catheter having an abrasive membercontained substantially within the catheter during positioning andabrasion, into the vascular system; and contacting the stenotic materialwith said abrasive member, whereby the stenotic material is abraded; andcollecting abraded stenotic material by means of flushing and aspirationwithin the catheter.
 8. A method according to claim 7, wherein theabraded stenotic material is withdrawn from the housing by aspiration.9. A method according to claim 8, wherein the abraded stenotic materialis withdrawn from the housing by a combination of flushing andaspiration.
 10. A method according to claim 7, further comprisingimaging the vascular system with an ultrasonic transducer, mounted onthe abrasive member.
 11. A method according to claim 7, furthercomprising inflating at least one inflatable balloon attached to thehousing so that the stenotic material penetrates the aperture of thehousing.
 12. A method according to claim 7, wherein the abrasive memberis contacted by translation in combination with rotation.
 13. A methodfor removing the stenotic material from a patient's vascular systemcomprising the steps of:introducing a catheter, said catheter having anabrasive member contained substantially within the catheter duringpositioning and abrasion, into the vascular system; contacting thestenotic material with said abrasive member, whereby the stenoticmaterial is abraded and collected by the catheter; and monitoring theextent of removal of stenotic material concurrent with or subsequent tothe abrasion process.
 14. A method according to claim 13, wherein theabraded stenotic material is withdrawn from me housing by aspiration.15. A method according to claim 14, wherein the abraded stenoticmaterial is withdrawn from the housing by a combination of flushing andaspiration.
 16. A method according to claim 13, further comprisingimaging the vascular system with an ultrasonic transducer, mounted onthe abrasive member.
 17. A method according to claim 13, furthercomprising inflating at least one inflatable balloon attached to thehousing so that the stenotic material penetrates the aperture of thehousing.
 18. A method according to claim 13, wherein the abrasive memberis contacted by translation in combination with rotation.
 19. A methodfor removing the stenotic material from a patient's vascular systemcomprising the steps of:introducing a catheter, said catheter having anabrasive member contained substantially within the catheter duringpositioning and abrasion, into the vascular system; contacting thestenotic material with said abrasive member, whereby the stenoticmaterial is abraded; collecting abraded stenotic material by means offlushing and aspiration within the catheter; and monitoring the extentof removal of stenotic material concurrent with or subsequent to theabrasion process.
 20. A method according to claim 19, wherein theabraded stenotic material is withdrawn from the housing by aspiration.21. A method according to claim 20, wherein the abraded stenoticmaterial is withdrawn from the housing by a combination of flushing andaspiration.
 22. A method according to claim 19, further comprisingimaging the vascular system with an ultrasonic transducer, mounted onthe abrasive member.
 23. A method according to claim 19, furthercomprising inflating at least one inflatable balloon attached to thehousing so that the stenotic material penetrates the aperture of thehousing.
 24. A method according to claim 19, wherein the abrasive memberis contacted by translation in combination with rotation.